1、外文資料：Prestressed Concrete BuildingsPrestressed concrete has been widely and successfully applied to building construction of all types. Both precast pretensioned members and cast-tensioned structures are extensively employed, sometimes in competition with one another, most effectively in combination

2、 wit each other.Prestressed concrete offers great advantages for incorporation in a total building. It is perhaps the “integratspe”ts of these, that is, structure plus other functions, which have made possible the present growth in use of prestressed concrete buildings. These advantages include the

3、following: Structural strength; Structure rigidity; Durability; Mold ability, into desired forms and shapes; Fire resistance; Architectural treatment of surfaces; Sound insulation; Heat insulation; Economy; Availability, through use of local materials and labor to a high degree.Most of the above are

4、 also properties of conventionally reinforced concrete. Presrressing, however, makes the structural system more effective by enabling elimination of the technical of difficulty, e.g., cracks that spoil the architectural treatment. Prestressing greatly enhance the structure efficiency and economy per

5、mitting longer spans and thinner elements. Above all, it gives to the architect-engineer a freedom for variation and an ability to control behavior under service conditions.Although prestressed concrete construction involves essentially the same consideration and practices as for all structures, a n

6、umber of special points require emphasis or elaboration.The construction engineer is involved in design only to a limited extent. First, he muse be able to furnish advice to the architect and engineer on what can he done. Because of his specialized knowledge of techniques relating to prestressed con

7、crete construction, he supplies a very needed service to the architect-engineer.Second, the construction engineer may be made contractually responsible for the working drawings; that is, the layout of tendons, anchorage details, etc. It is particularly important that he gives careful attention to th

8、e mild steel and concrete details to ensure these are compatible with his presressing details.Third, the construction engineer is concerned with temporary stresses, stresses at release, stresses in picking, handling and erection, and temporary condition prior to final completion of the structure, su

9、ch as the need of propping for a composite pour.Fourth, although the responsibility for design rests with the design engineer, nevertheless the construction engineer is also vitally concerned that the structure be successful form the point of view of structural integrity and service behavior. Theref

10、ore he will want to look at the bearing and connection details, camber, creep, shrinkage, thermal movements, durability provisions, etc., and advise the design engineer of any deficiencies he encounters.Information on new techniques and especially application of prestressing to buildings are extensi

11、vely available in the current technical literature of national and international societies. The International Federation of Prestressing(I.F.P)has attempted to facilitate the dissemination of this information by establishing a Literature Exchange Service, in which the prestressing journals of some t

12、hirty countries are regularly exchanged. In addition, an Abstract is published intermittently by I.F.P The Prestressed Concrete Institute(USA)regularly publishes a number of journals and pamphlets on techniques and applications, and procedures are set up for their dissemination to architects and eng

13、ineers as well as directly to the construction engineer. It is important that he keep abreast of these national and worldwide developments, so as to be able to recommend the latest and best that is available in the art, and to encourage the engineer to make the fullest and most effective use of pres

14、tressed concrete in their buildings.With regard to working drawings, the construction engineer must endeavor to translate the design requirements into the most practicable and economical details of accomplishment, in such a way that the completed element or structure fully complies with the design r

15、equirement; for example, the design may indicate only the center of gravity of prestressing and the effective prestress force. The working drawing will have to translate this into tendons having finite physical properties and dimensions. If the center of gravity of pre-stressing is a parabolic path

16、then, for pre-tensioning, and approximation by chords is required, with hold-down points suitably located.The computation of pre-stress losses, form transfer stress to effective stress, must reflect the actual manufacturing and construction process used, as well as thorough knowledge of the properti

17、es of the particular aggregates and concrete mix to be employed.With post-tensioning, anchorages and their bearing plates must be laid out in their physical dimension. It is useful in the preparation of complex anchorage detail layouts to use full-scale drawings, so as to better appreciate the conge

18、stion of mild steel and anchorages at the end of the member. Tendons and reinforcing bars should be shown in full size rather than as dotted lines. This will permit consideration to be given as to how the concrete can be placed and consolidated.The end zone of both pre-tensioned and post-tensioned c

19、oncrete members subject to high transverse or bursting stresses. These stresses are also influenced by minor concrete details, such as chamfers. Provision of a grid of small bars (sometimes heavy wire mesh is used), as close to the end of a girder as possible, will help to confine and distribute the

20、 concentrated forces. Closely spaced stirrups and/or tightly spaced spiral are usually needed at the end of heavily stressed members. Recent tests have confirmed that closeness of spacing is much more effective than increase in the size of bars. Numerous small bars, closely spaced, are thus the best

21、 solution.Additional mild-steel stirrups may also be required at hold-down points to resist the shear. This is also true wherever post-tensioned tendons make sharp bends. Practical consideration of concretion dictates the spacing of tendons and ducts. The general rules are that the clear spacing sma

22、ll be one-and-one-half times the maximum size of coarse aggregate. In the overall section, provision must be made for the vibrator stinger. Thus pre-stressing tendons must either be spaced apart in the horizontal plane, or, in special cases, bundled.In the vertical plane close contact between tendon

23、s is quite common. With post-tensioned ducts, however, in intimate vertical contact, careful consideration has to be given to prevent one tendon form squeezing into the adjacent duct during stressing. This depends on the size of duct and the material used for the duct. A full-scale layout of this cr

24、itical cross section should be made. Usually, the best solution is to increase the thickness ( and transverse strength ) of the duct, so that it will span between the supporting shoulders of concrete.As a last restort it may be necessary to stress and grout one duct before stressing the adjacent one

25、. This is time-consuming and runs the risks of grout blockage due to leaks from one duct to the other. Therefore the author recommends the use of heavier duct material, or else the respacing of the ducts. The latter, of course, may increase the prestressing force required.中文翻譯：預(yù)應(yīng)力混凝土建筑預(yù)應(yīng)力混凝土已經(jīng)廣泛并成功地

26、用于各種類(lèi)型的建筑。無(wú)論預(yù)制先拉構(gòu) 件，還是現(xiàn)澆后張構(gòu)件都已大量應(yīng)用，在應(yīng)用二者時(shí)會(huì)相互競(jìng)爭(zhēng)，但結(jié)合應(yīng) 用效率更高。在預(yù)應(yīng)力混凝土為一棟建筑物的總體結(jié)合提供了方便。或許正是因?yàn)槠湓?建筑結(jié)構(gòu)及其他功能結(jié)合上所起的作用，才使得預(yù)應(yīng)力混凝土應(yīng)用得以推 廣。其優(yōu)點(diǎn)體系在下述各項(xiàng)；結(jié)構(gòu)強(qiáng)度；結(jié)構(gòu)港督；耐久性；可塑性，可制 成所需求的方式和形狀；抗火性；表面的建筑處理；隔聲；絕熱；經(jīng)濟(jì)性； 可行性，可通過(guò)使用本地原料和勞動(dòng)力達(dá)到較高的程度。上面大都是傳統(tǒng)鋼筋混凝土具有的特點(diǎn)。然而，預(yù)應(yīng)力通過(guò)對(duì)建筑有破 壞作用的裂縫等缺陷源的消除，而使結(jié)構(gòu)系統(tǒng)更加有效。由于允許采用較長(zhǎng) 和較薄構(gòu)件，預(yù)應(yīng)力大大提高了結(jié)構(gòu)的

27、效率和經(jīng)濟(jì)性。更重要的是，它為建 筑師提供了一種變化的自由，以及在各種服務(wù)條件下的行為控制能力。盡管預(yù)應(yīng)力混凝土結(jié)構(gòu)在本質(zhì)上有著和所有結(jié)構(gòu)一樣的設(shè)計(jì)考慮和操 作，但應(yīng)重視和推敲一下特殊點(diǎn)。施工工程師在設(shè)計(jì)中參與的工作是有限的。首先，他必須能夠向建筑師 和工程師提供可行性的建議。由于其具有預(yù)應(yīng)力混凝土施工方面的專(zhuān)業(yè)技術(shù) 知識(shí)，他將為建筑師和工程師提供非常必要的服務(wù)。其次，施工工程師應(yīng)通曉施工圖。例如鋼筋的放置及錨定細(xì)節(jié)的等。尤 為重要的是他應(yīng)對(duì)鋼筋和混凝土細(xì)節(jié)給予足夠重視，以使其能夠與預(yù)應(yīng)力細(xì) 節(jié)相一致。第三，施工工程師應(yīng)該在結(jié)構(gòu)完工之前，注重鋼筋的臨時(shí)應(yīng)力、松弛應(yīng) 力、截取、加工和安裝階段的應(yīng)

28、力，以及臨時(shí)條件，如復(fù)合灌注時(shí)所需的支 柱支撐。第四，盡管設(shè)計(jì)任務(wù)是設(shè)計(jì)工程師的工作職責(zé)，不過(guò)施工工程師應(yīng)該從 結(jié)構(gòu)整體及使用功能上把握結(jié)構(gòu)的可行性。因此他會(huì)關(guān)注承載和連接細(xì)節(jié)、 撓度、蠕變、收縮、熱運(yùn)動(dòng)及耐久性保證等，并向設(shè)計(jì)工程師提供相應(yīng)的建 議。當(dāng)今國(guó)內(nèi)外，新技術(shù)尤其是預(yù)應(yīng)力在建筑物上的應(yīng)用技術(shù)，已經(jīng)廣泛使 用。國(guó)際預(yù)應(yīng)力聯(lián)盟試圖通過(guò)建立文化交流服務(wù)來(lái)散布這些信息，大約 30 多個(gè)國(guó)家的預(yù)應(yīng)力雜志進(jìn)行了交流。并且，該聯(lián)盟還定期發(fā)布一些摘要信息。 美國(guó)的“預(yù)應(yīng)力混凝土結(jié)構(gòu)”定期發(fā)布一些關(guān)于技術(shù)及應(yīng)用的雜志和手冊(cè)， 同時(shí)還建立了將其傳播給建筑師、工程師以及施工人員的程序。這種與國(guó)內(nèi) 和國(guó)際發(fā)展接軌的工作有著很重要的意義，它能夠使技術(shù)保持最新和最